Unable to enter credit memo due to response ‘Netsuite.com is not responding due to a long run scripts, and you can stop scripts’

You are getting this response because possibly, the total number of open invoices exceeded the Row Limit or maximum number of transactions a sublist can accommodate 

Below are the steps that you may take to avoid the problem. You have to filter the invoices by date to narrow down the result.

1. Please navigate to Transactions > Customers > Issue Credit Memos

2. Go to Items Tab > Apply Subtab

3. Click Customize button

4. Check the Include checkbox for 'Date' and 'Number/ID' under Additional Filters Tab

5. Click Save.

6. Go back to Items Tab > Apply Subtab

7. Set the Date = This Month or  any preferred date range

8. Alternatively, you can type the Invoice number on the Number/ID filter.